OpenRouter / OpenAI API

Fix OpenRouter BYOK prompt caching disabled — excessive token costs for Claude models in agent mode

Resolve OpenRouter silently disabling prompt caching for Anthropic Claude models via BYOK, causing full-context resends at full price in long agent sessions Includes evidence for OpenRouter troubleshooting demand.

Source-backed Last updated May 16, 2026 1 source Needs local verification

Category: OpenAI API
Error signature: OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode
Quick fix: Compare the failing environment with a known working setup, then change one configuration value at a time.
Updated: May 16, 2026
Verification status: Source-backed
Evidence: 1 public source URL

Before you change production

This page includes public source URLs in the imported troubleshooting record. Compare those references with your version and environment before applying changes.

Reproduce the smallest failing action and save non-secret logs before changing configuration.
Check versions for OpenRouter, related SDKs, package managers, CI runners, and hosting providers.
Change one setting or dependency at a time, then rerun the same failing command or request.
Avoid destructive commands, credential rotation, billing changes, or security relaxations without a rollback plan.

What this error means

OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode is a OpenRouter failure pattern reported for developers trying to resolve openrouter silently disabling prompt caching for anthropic claude models via byok, causing full-context resends at full price in long agent sessions. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

microsoft/vscode#312939 — When using OpenRouter BYOK with Claude models in GitHub Copilot, prompt caching is silently disabled. Every agentic request re-sends full conversation context at full price. High billing impact for paid users. Category mapping: OpenRouter with API compatibility issue → OpenAI API (context-dependent mapping per SKILL.md).

Common causes

microsoft/vscode#312939 — When using OpenRouter BYOK with Claude models in GitHub Copilot, prompt caching is silently disabled. Every agentic request re-sends full conversation context at full price. High billing impact for paid users. Category mapping: OpenRouter with API compatibility issue → OpenAI API (context-dependent mapping per SKILL.md).

Quick fixes

Confirm the exact error signature matches OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode.
Check the OpenRouter account, local tool state, and provider configuration involved in the failing workflow.
Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

Verify the command, editor, extension, or API client that produced the error.
Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

Capture the exact error message and the command, editor action, or request that triggered it.
Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
Review the source evidence below and compare it with your environment.
Apply one change at a time and rerun the smallest failing action.
Keep the working fix documented for the team or deployment environment.

How to prevent it

Keep provider/tool configuration documented.
Record non-secret diagnostics such as tool version, provider name, model name, and command path.
Add a lightweight check before CI or production workflows depend on the tool.

Diagnostic flow for this page

Match OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode exactly before applying the quick fix.
Compare the failing environment with OpenRouter versions, account scope, provider settings, and deployment context.
Check the listed common causes in order, starting with the cause that best matches your logs.
Use the evidence status below to decide whether to confirm against public sources or official documentation.
Apply one reversible change, rerun the smallest failing action, and keep rollback notes.

FAQ

What does OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode mean in OpenRouter?

OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode indicates the workflow described by "Fix OpenRouter BYOK prompt caching disabled — excessive token costs for Claude models in agent mode" failed in a OpenAI API context. Start by confirming the exact signature and the component that emitted it.

What should I check first for OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode?

Check whether this cause matches your environment: microsoft/vscode#312939 — When using OpenRouter BYOK with Claude models in GitHub Copilot, prompt caching is silently disabled. Every agentic request re-sends full conversation context at full price. High billing impact for paid users. Category mapping: OpenRouter with API compatibility issue → OpenAI API (context-dependent mapping per SKILL.md).

Is the OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode guidance source-backed?

The "Fix OpenRouter BYOK prompt caching disabled — excessive token costs for Claude models in agent mode" page is labeled source-backed. It has 1 public source URL from github.com, so use that evidence status when deciding how much additional verification you need.

When should I avoid the quick fix for OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode?

For "Fix OpenRouter BYOK prompt caching disabled — excessive token costs for Claude models in agent mode", avoid applying "Compare the failing environment with a known working setup, then change one configuration value at a time." when the error text differs, the affected version or provider is different, or the change would touch credentials, billing, DNS, production deploy settings, or irreversible data.

What should I collect before debugging OpenRouter BYOK: Claude models do not benefit from prompt caching, causing excessive token costs in agent mode?

For "Fix OpenRouter BYOK prompt caching disabled — excessive token costs for Claude models in agent mode", collect the failing OpenRouter command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.